Federal law enforcement authorities have authority, given to them under various parts of the United States Code (U.S.C.). Federal law enforcement officers enforce various laws, generally at only the federal level. There are exceptions, with some agencies and officials enforcing state and tribal codes. Most are limited by the U.S. Code to investigating matters that are explicitly within the power of the federal government. Some federal investigative powers have become broader in practice, since the passage of the USA PATRIOT Act in October 2001.

While the majority of federal law enforcement employees work for the departments of Justice and Homeland Security, there are dozens of other federal law enforcement agencies under the other executive departments, as well as under the legislative and judicial branches of the federal government.

In 2004, federal agencies employed approximately 105,000 full-time personnel authorized to make arrests and carry firearms in the 50 states and the District of Columbia. Compared with 2002, employment of such personnel increased by 13%.

Nationwide, there were 36 federal officers per 100,000 residents. Outside the District of Columbia, which had 1,662 per 100,000, State ratios ranged from 90 per 100,000 in Arizona to 7 per 100,000 in Iowa.

As of 2004, about 3 in 4 federal law enforcement officers working outside the Armed Forces were employed within the Department of Homeland Security or the Department of Justice.

Women accounted for 16% of federal officers in 2004, an increase from 14.8% in 2002.

A third (33.2%) of federal officers were members of a racial or ethnic minority in 2004. This included 17.7% who were Hispanic or Latino, and 11.4% who were black or African American. In 2002, racial or ethnic minorities officers comprised 32.4% of federal officers.

Twenty-seven federal offices of inspector general (IG) employed criminal investigators with arrest and firearm authority in 2004. Overall, these agencies employed 2,867 such officers in the 50 states and District of Columbia.[4]